From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753420AbaKLWSg (ORCPT ); Wed, 12 Nov 2014 17:18:36 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:23131 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751865AbaKLWSf (ORCPT ); Wed, 12 Nov 2014 17:18:35 -0500 Date: Wed, 12 Nov 2014 17:18:13 -0500 From: Konrad Rzeszutek Wilk To: Juergen Gross Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, david.vrabel@citrix.com, boris.ostrovsky@oracle.com, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com Subject: Re: [PATCH V3 6/8] xen: Hide get_phys_to_machine() to be able to tune common path Message-ID: <20141112221813.GE7549@laptop.dumpdata.com> References: <1415684626-18590-1-git-send-email-jgross@suse.com> <1415684626-18590-7-git-send-email-jgross@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415684626-18590-7-git-send-email-jgross@suse.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 11, 2014 at 06:43:44AM +0100, Juergen Gross wrote: > Today get_phys_to_machine() is always called when the mfn for a pfn > is to be obtained. Add a wrapper __pfn_to_mfn() as inline function > to be able to avoid calling get_phys_to_machine() when possible as s/when/where/ > soon as the switch to a linear mapped p2m list has been done. But your inline function still calls get_phys_to_machine? > > Signed-off-by: Juergen Gross > --- > arch/x86/include/asm/xen/page.h | 27 +++++++++++++++++++++------ > arch/x86/xen/mmu.c | 2 +- > arch/x86/xen/p2m.c | 6 +++--- > 3 files changed, 25 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h > index 28fa795..07d8a7b 100644 > --- a/arch/x86/include/asm/xen/page.h > +++ b/arch/x86/include/asm/xen/page.h > @@ -59,6 +59,22 @@ extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops, > struct page **pages, unsigned int count); > extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn); > > +/* > + * When to use pfn_to_mfn(), __pfn_to_mfn() or get_phys_to_machine(): > + * - pfn_to_mfn() returns either INVALID_P2M_ENTRY or the mfn. In case of an > + * identity entry the identity indicator will be cleared. Why don't you say : In case of identity PFN the same PFN is returned. But you did miss that also the FOREIGN_FRAME_BIT is cleared. > + * - __pfn_to_mfn() returns the found entry of the p2m table. A possibly set s/of the/in the/ > + * identity indicator will be still set. __pfn_to_mfn() is encapsulating .. be still set if the PFN is an identity one. > + * get_phys_to_machine() and might skip that function if possible to speed > + * up the common path. How is is skipping that function? The patch below does no such thing? > + * - get_phys_to_machine() is basically the same as __pfn_to_mfn(), but > + * without any short cuts for the common fast path. Right. Perhpas we should call it 'slow_p2m' instead of the 'get_phys_to_machine'. > + */ > +static inline unsigned long __pfn_to_mfn(unsigned long pfn) > +{ > + return get_phys_to_machine(pfn); > +} > +